Vestibular disorders exact a huge toll in lost productivity and quality of life. The bilateral loss of vestibular function is currently a disorder without effective treatment other than rehabilitative strategies which cannot restore normal vestibulo-ocular or vestibulo-spinal reflexes. Due to the extraordinary success of cochlear implants, there has been a major effort to develop a similar neural prosthesis for the diseased vestibular system. We have developed a vestibular neurostimulator, studied it in rhesus monkeys, and performed four human implants under an FDA investigational device exemption for the treatment of uncontrolled Meniere's disease. Our four human subjects have had profound hearing loss postoperatively and significant loss of electrically-evoked responses has been observed in all of our human subjects and some of our monkeys over months postoperatively. We propose a modification to our existing devices to provide greater stability within the labyrinth and to partly restore hearing in the implanted ear. We also propose a detailed series of longitudinal human studies with the new design to characterize the function of a gyroscopic sensor that we have developed for the treatment of vestibular loss as well as safety studies of the new design in non-human primates. These studies will greatly enhance our understanding of the effects of a vestibular implant in humans and allow us to develop an investigational device exemption for the treatment of uncompensated unilateral and bilateral vestibular loss.